Hydrogen (H2) is expected to be one of the most promising secondary energy resources that can contribute to the mitigation of global warming. H2 can be synthesized from biomass feedstock as Bio-H2, which can contribute to greenhouse gas emission mitigation. However, the low energy density of Biomass limits the collection of the feedstock based on the life-cycle assessment methodology. Furthermore, for successful operation, small-scale Bio-H2 plants must be used. Thus, a Bio-H2 plant faces two challenges: 1) the need for auxiliary power negatively affects production efficiency and increases eco-burden. In particular, pressure swing adsorption (PSA) used for H2 purification requires high power consumption, 2) a large amount of heat is lost. To overcome these limitations, we improved a previous Bio-H2 plant by introducing 2-step PSA and a waste heat recovery system (WHR) to reduce the auxiliary power consumption and to compensate the auxiliary power demand. It was found that, the improved plant reduced the auxiliary power demand by 18.9%, and 7.2% of the required power was compensated by the WHR system. Furthermore, all environmental indicators were improved compared to those for the conventional plant.
In this study, we focused on the purification of biohydrogen by indirect pyrolysis. Syngas typically contains small amounts of impurities (e.g., NH3), which negatively affect the fuel cell operation. Earlier, our group has developed removal technologies using solid adsorbents. Additionally, we estimated the adsorption performance considering environmental aspects based on life cycle assessment. In this study, we focused on the NH3 removal capacities of two different adsorbents: hydroxyl aluminum silicate clay (HAS-Clay) and natural clay (KanumaClay). We fabricated an experimental apparatus to evaluate the adsorption performance. The results show that the maximum adsorption of HAS-Clay is 2.90 g NH3/100 g sorbent, whereas a maximum adsorption of 2.02 g NH3/100 g sorbent was obtained by using Kanuma-Clay. Both adsorbents have the same allophane composition, which contributes to the adsorption performance. However, the environmental impacts of HAS-Clay and Kanuma-Clay differ. Thus, we evaluated their eco-burdens on the NH3 removal.
The oil palm empty fruit bunch (EFB) is a rich carbon-source material that can be considered as a valuable candidate for several applications. Recently, EFB has been used as an organic compost fertilizer in oil palm plantations. The life cycle assessment (LCA), life cycle cost (LCC), and cumulative energy demand (CED) were used to evaluate the feasibility of EFB as a raw material for dissolving pulp and furfural co-production. An additional techno-economic assessment was performed on realistic industrial-scale process conditions for cost calculation. In the production of 1 kg dissolving pulp with the co-production of 0.01 kg furfural, -1.218 kg CO2 eq of global warming potential (GWP100), -0.006 kg SO2 eq of acidification potential (AP), -0.002 kg PO43- eq of eutrophication potential (EP), -0.054 kg 1,4-DB eq of human toxicity potential (HTP) and 1.887 MJ of cumulative energy demand (CED) were generated. The economic assessment indicated that the production of 1 kg dissolving pulp in the proposed product system resulted in earnings of 71.11 JPY based on LCC methodology and earnings of 54.44 JPY in the techno-economic assessment simulation after 15 years. The application of the waste-to-product concept for EFB via biorefinery processes, such as dissolving pulp and furfural co-production, offer advantages in terms of economic, environmental, and energy requirements.
In the paper production industry, typically, waste from the papermaking process, such as woody waste, waste reject, and paper sludge, is used for internal energy recovery. Our research focuses on paper sludge that has high moisture content. Our previous study that showed that hydrothermal treatment can convert paper sludge into solid fuel. In this study, we calculated the CO2 emissions from the paper sludge valorization to generate electricity in actual paper mills in Thailand. As a result, when hydrothermal treatment was applied on paper sludge and the product was cofired with coal, it was better in terms of an environmental perspective and technical feasibility in the case of the small- and medium-size boilers, 50 and 80 t/h.
The sorption behaviors of SO2 and NH3 gases on sewage sludge char were investigated using a commercial thermodynamic equilibrium calculation software and lab-scale fixed-bed reactor in order to develop the desulfurization and deodorization technologies in the new energy saving sludge treatment system combining with bio-drying and carbonization technologies. The enthalpy change of the neutralization reaction of SO2 with NH3 (SO2 + 2NH3 + H2O + 1/2O2 = (NH4)2SO4) was calculated to result in being a lower enthalpy change with a lower temperature. The results show in the thermodynamic equilibrium state of 2SO2, 4NH3, 2H2O, and O2 to form (NH4)2SO4 as solid-phase species under the conditions from 0 to 200 °C. The gas activation of the char and a longer space time of SO2 and NH3 gases in the char increased the sorbed amounts of the gases into the char. The molar ratio of NH3 to SO2 in a feed gas to be 2, which is the stoichiometric molar ratio for the formation of ammonium sulfate, was the better condition for the gas-phase reaction and gas sorption of SO2 and NH3 gases into the char.